Slow flow in regenerating C-fibers.

An identical rate of slow flow was measured in 3 different populations of regenerating C-fibers which have very different growth abilities as expressed by a 6-fold difference in their elongation velocities. At 21 degrees C, this rate of slow flow is 3.5 times faster than the rate measured in intact nerves and is identical to the elongation velocity of the most rapidly regenerating fibers. Slow flow may constitute the upper limit of the elongation velocity of a regenerating axon but other factors determined by the perikaryon (such as protein synthesis) might prevent the neuron from reaching the maximal growth rate.